As the storage densities in magnetic recording media increase, the read/write magnetic heads must be positioned on the desired tracks with increasing accuracy. Secondary (piggyback) microactuators have been proposed for increasing the tracking accuracy and speed for magnetic recording heads.
U.S. Pat. Nos. 5,521,778, 5,189,578, 5,177,652, and 4,858,040, as well as the article by Koshida in IBM Technical Disclosure Bulletin 31(2):220-221 (1988), describe various arm assemblies comprising piezo-electric secondary actuators. While such actuators may be used for finely positioning magnetic heads, piezo-electric elements generally have low reliability and require higher voltages than used in conventional disk drives.
An article by Koganezawa et al. in IEEE Trans. Magn. 32(5):3908-3910 (1996) describes a flexural piggyback electromagnetic actuator. A flexural cross-shaped spring connects a movable head mounting block to a fixed rigid arm. The head and suspension assembly is mounted on the head mounting block. A coil on the head mounting block is magnetically coupled to a permanent magnet on the rigid arm. The spring used by Koganezawa et al. is a high-aspect ratio, thin stainless steel structure, which is relatively difficult to manufacture.
In U.S. Pat. No. 5,657,188, Jurgenson et al. disclose a disk drive suspension having an electromagnetic actuator. Two coils mounted on the suspension generate a magnetic field in the plane of the suspension (the tracking plane). The magnetic field is applied to a movable pole connected to the suspension tip, to change the orientation of the suspension tip. The Jurgenson et al. system provides a relatively small surface area for the magnetic coupling between the coil and the movable pole, and consequently relatively limited actuating forces and range of motion. Moreover, adding a microactuator within the suspension may negatively affect system performance, which is in general limited primarily by suspension dynamics.